Weighing scales and peripheral equipment used in the food industry must meet stringent requirements regarding cleanability and hygienic safety. A typical area of application for these scales is in the production of foods. In this environment, the scale and the housing that encloses electronic components come into direct contact with the food products. The cleaning of these scales may among other methods involve the use of high-pressure cleaners. There needs to be assurance that the housing is sealed tight during the cleaning process and that for example contaminants are prevented from entering into the housing of the scale display, since the electronic components inside the housing could otherwise suffer damage. This requirement can be met with housing components made of stainless steel and by arranging a seal between the components. However, the manufacture of a stainless steel housing is subject to technical limitations. Due to these limits, the housing has a relatively large volume and the choices for the shape of the housing are limited. As a further drawback, the seal between two stainless steel elements can be susceptible to damage. The seal could be damaged especially when the housing is opened for maintenance work. As a consequence, there is a risk that the housing may no longer be sealed tight after a maintenance service has been performed. Due to leaks in the housing, water or cleaning agents could potentially penetrate into the housing during the cleaning process and cause damage to the electronic components.
There is an objective to provide a housing for electronic components which has a compact shape as well as the ability to stay reliably sealed.
This task is solved with a housing that comprises the features described in the independent patent claim. Further advantageous embodiments are presented in the dependent claims.
The disclosed housing, which serves to enclose electronic components for the control of a weighing scale, has a first housing part and a second housing part. The first and second housing parts are designed so that a first enclosed space is formed between them which serves to hold electronic components. Arranged between the first housing part and the second housing part is a fastening module having a first side and, opposite from the latter, a second side. The first side has a first circumferential seating ledge to receive the first housing part. The second side has a second circumferential seating ledge to receive the second housing part.
The shapes of the housing parts and of the fastening module need to be suitably selected, so that the two housing parts and the fastening module form an enclosed space to house electronic components.
The fastening module also functions as an intermediate part, possibly as an adapter, between the first and the second housing part. The two housing parts don't come into direct contact with each other. There is more flexibility for designing the seal between the housing parts and the fastening module. This has the advantage that the two housing parts do not have to be matched so closely to each other. As a result, there is greater latitude of design choices for the two housing parts. In particular, the inventive concept allows a more compact design of the display- and operating unit.
In an advantageous embodiment, the first circumferential seating ledge meets the first housing part in form-fitting contact. The first housing part has for example an essentially flat, planar surface in which the display- and operating unit is imbedded. Preferably, the display- and operating unit is also of an essentially planar configuration. The first circumferential seating ledge, likewise, has an essentially planar surface which works together with the planar surface of the first housing part through a form-fitting engagement. With this arrangement, it is possible to prevent contaminants from penetrating between the first housing part and the fastening module into the interior of the housing.
The fastening module can be releasably connected to the first housing part with at least one fastener means. A suitable fastener means is for example a screw. It is also possible to use a non-releasable connection between the fastening module and the first housing part, for example an adhesive. As a further possibility, the two parts could be connected to each other with a press fit. It is also possible to use a connection that can be released without tools, for example clips or snap fasteners.
The second circumferential seating ledge ideally has a continuous groove designed to receive a circumferential border edge of the second housing part. As an additional seal, there can be a sealing gasket arranged between the groove and the border edge. It is advantageous to fasten the sealing gasket to the second housing part through a fixed connection. This can be achieved for example with a liquid sealant which is injected into the groove where it solidifies. However, it is also possible to use a seal which is not permanently connected to the housing part. A standard seal gasket and/or an O-ring can be used for this purpose.
The second housing part in a possible embodiment is tub-shaped, and a circumferential separating wall is formed on the fastening module. The separating wall is rimmed by a circumferential edge. When the housing is in the closed state, the circumferential edge of the separating wall conforms to an inside surface of the tub-shaped second housing part, so that inside the first enclosed space there is a second enclosed space being formed which serves to house electronic parts. The second enclosed space is thus part of the first space. The second enclosed space is delimited by the fastening module and a part of the tub-shaped second housing part. The second space is encircled by a ring-shaped part of the first space. The ring-shaped part surrounds the second space like a buffer zone. No sensitive electronic components should be arranged in this ring-shaped part.
This configuration has the advantage that the second enclosed space is additionally protected from the entry of contaminants by the surrounding part of the first space. The electronic components arranged in the second space are thus protected from mechanical and chemical influences.
The arrangement of a seal gasket between the circumferential edge of the separating wall and the second housing part provides an additional barrier against the penetration of contaminants into the second space. Even if the first, outer seal gasket should become damaged by extraneous influences, the second, inner seal gasket still protects the electronic components from influences of the ambient environment.
With the use of the first and the second seal gasket, there is a greater probability that the housing still remains leak-tight after it has been opened and reclosed, because it is less probable that the first and second seals could get damaged simultaneously. In addition, the first seal protects the second seal from influences of the ambient environment. Even if the first seal is partially damaged, it still offers protection to the second seal against extraneous influences, particularly during an aggressive cleaning process.
With the use of the first and the second seal gasket, the specifications that the first seal gasket must meet are less demanding, as the second seal gasket serves as a backup. The requirements for the attachment of the second housing part to the fastening module will likewise be less severe. The second housing part can therefore be attached to the fastening module with a less elaborate connection, which has the advantage that the second housing part can also be removed and reattached in a simpler way. As an advantageous result, when performing maintenance work, the housing can be opened and closed again more quickly.
With preference, the fastening module is made essentially of a synthetic material, which offers the advantage that it makes the fastening module simple and cost-effective to manufacture. A synthetic material has the further advantage, that very complex shapes can be produced in a simple manner. As a consequence, when choosing the shape of the fastening module, many possibilities are open. The shape of the fastening module can in particular be adapted easily to the shapes of the two housing parts.
In an advantageous embodiment, the first housing part and the second housing part are made essentially of metal, specifically of chromium steel. Metal has the advantage that the housing will be easy to clean, however with the drawback that the manufacture of complex shapes is expensive.
The housing parts can be made by welding. However, a less favorable aspect of welding is that contaminants may accumulate at the weld seams.
Ideally, the first housing part and/or the second housing part is made of one integral piece. A seamless construction of the first and/or second housing part is likewise advantageous. The problem of accumulations along the seams can thus be avoided. The seamless housing can be produced for example by deep-drawing.
The housing enclosures that are used in the food industry must meet stringent requirements in regard to their cleanability. The radii at their corners and edges should therefore be as large as practically possible, ideally larger than 6 mm. The housing should have no slots or crevices. If the housing parts are castings, one needs to make certain that no air cavities are formed. Undercuts should also be avoided.
In a preferred embodiment, the second housing part is rigidly attached to a vertically oriented pedestal, and in the opened state of the housing the first housing part is releasably connected to the second housing part by means of a holder module. When the housing is opened, the first housing part remains tied to the second housing part through the holder module. If no holder module were used, the first housing part could possibly hang from electrical cables through which the electronic components mounted on the second housing part are connected to the display- and operating unit. This could cause damage to the electrical cables or the electronic components. The use of the holder module has the advantage that in order to perform service work on the electronic components, the first housing part does not have to be completely removed, but still remains connected to the second housing part without the risk of damage to the electrical cables or the electronic components.
It is possible to make the holder module of at least one flexible material which is fastened to the first as well as to the second housing part. The flexible material can be for example a synthetic material, a metal, or a textile material. The holder module can include a metallic wire, a textile ribbon, or a polymer element. To attach the holder module to the first and/or second housing part one could for example use screws. However, for the attachment to at least the first or the second housing part it is advantageous to use a fastener means that can be disconnected without using a tool, because this will allow the housing parts to be separated from each other quickly and easily in case this becomes necessary.
The holder module includes a connector element with a hinge lug and a hinge pin cooperating with the hinge lug. The connector element is solidly attached to the first housing part and the hinge pin to the second housing part. However, other configurations of the connector element are likewise conceivable.